Answer this question truthfully
### Question: What causes CMV pneumonitis?
### Response: CMV pneumonia is caused by a member of a group of herpes-type viruses. Infection with CMV is very common. Most humans are exposed to CMV in their lifetime, but typically only individuals with weakened immune systems become ill from CMV infection
Usually CMV produces no symptoms, but serious CMV infections can occur in people with weakened immune systems from conditions such as:
AIDS. Bone marrow transplant. Organ transplant. Chemotherapy or other treatments that suppress the immune system.
In people who have had organ and bone marrow transplants, the risk of infection is greatest 5 - 13 weeks after the transplant.